Device for cooling an interior of a motor vehicle

ABSTRACT

The invention relates to a device for cooling a vehicle interior with a secondary circuit ( 26 ) for transferring the cold produced in an evaporator ( 24 ) of a primary refrigerating circuit ( 14 ) of a refrigerating unit ( 12 ) by means of a refrigerating medium to at least one heat transfer device ( 34 ) for cooling the air to be fed into the vehicle interior, the secondary circuit ( 26 ) having a main circuit ( 36 ) and an auxiliary circuit ( 40 ) containing the heat transfer device ( 34 ), which are coupled by a four-way valve ( 56 ), by means of which an adjustable proportion of the flow of refrigerating medium can be diverted from the main circuit ( 36 ) and fed into the auxiliary circuit ( 40 ). In order to provide an improved device for cooling, in particular one that can be produced at a more reasonable cost, it is proposed that an inner heat exchanger ( 80 ) should be provided in the auxiliary circuit ( 40 ), allowing heat exchange to take place between a feed ( 60 ) and a return ( 62 ). This makes it possible to dispense with the use of a circulation pump in the auxiliary circuit.

BACKGROUND OF THE INVENTION

The invention relates to a device for cooling an interior of a motorvehicle.

A device of this kind for interior cooling is known from DE 198 38 880and has a primary refrigerating circuit, which comprises a compressor, acondenser, an expansion element and an evaporator. The evaporatortransfers the cold (i.e., a temperature conditioned flow mass such asvapor) produced in the primary circuit by the evaporator to arefrigerating medium in a secondary circuit. The secondary circuit has amain circuit and an auxiliary circuit, which are coupled by a four-wayvalve, allowing an adjustable proportion of the flow of refrigeratingmedium to be diverted from the main circuit and fed into the auxiliarycircuit. Arranged in the auxiliary circuit is a heat transfer device,which is used to cool the air to be fed to the vehicle's interior.

Also provided in the auxiliary circuit is a circulation pump. Thisensures that there is always a high mass flow in the auxiliary circuitcomprising the four-way valve, the feed, the heat transfer device andthe return, it being possible to control the high mass flowindependently of the mass flow of refrigerating medium in the maincircuit, i.e. independently of the position of the four-way valve. If,for example, only a low refrigerating capacity is required, the four-wayvalve is set in such a way that only a small proportion of the very coldmass flow of refrigerating medium is diverted from the main circuit andfed into the auxiliary circuit. This small proportion is fed back intothe main circuit via the return. If there were no circulation pump, themass flow of refrigerating medium in the auxiliary circuit would be lowin accordance with the proportion fed in through the four-way valve, andthe refrigerating medium would flow only slowly through the heattransfer device. This would have the disadvantage that the refrigeratingmedium, which is very cold in the feed, could cause icing of the heattransfer device, at least in the region of an inlet of the heat transferdevice. The air cooled by the heat transfer device would at least bevery “stratified”, i.e. exhibit a large temperature difference over thecross section of an air outlet region of the heat transfer device. Thehigh susceptibility to gradients that causes this stratification andicing, i.e. a large temperature gradient of the refrigerating medium inthe auxiliary circuit, is avoided by the high mass flow that can beachieved by means of the circulation pump. However, an additionalcirculation pump in the auxiliary circuit is very costly since it leadsto costs for materials and requires a suitable means of control.

Based on this prior art, it is the object of the invention to provide animproved device for cooling an interior, in particular one that can beproduced at lower cost.

SUMMARY OF THE INVENTION

In accomplishing the objects of the invention, there has been provided,according to one aspect of the invention, a device for cooling a vehicleinterior comprising a cooling device for cooling an interior of avehicle, comprising:

a primary refrigerating circuit comprising an evaporator for providing atemperature conditioned flow; and

a secondary circuit operatively coupled to said primary refrigeratingcircuit, said secondary circuit carrying a refrigerating medium to whichthe temperature conditioned flow from said evaporator is provided, saidsecondary circuit comprising:

a main circuit;

an auxiliary circuit operatively coupled with said main circuit; and

an adjustable valve for controlling flow of the refrigerating mediumbetween said main circuit and said auxiliary circuit,

wherein said auxiliary circuit comprises (i) at least one heat transferdevice for receiving said refrigerating medium and cooling air to befeed into the vehicle interior, and (ii) an inner heat exchangeroperatively coupled with said heat transfer device for increasing thetemperature of the refrigerating medium provided to said heat transferdevice.

According to another aspect of the present invention, there is provideda device for cooling comprising a vehicle air conditioning unitcomprising:

a cooling device comprising:

a primary refrigerating circuit comprising an evaporator for providing atemperature conditioned flow; and

a secondary circuit operatively coupled to said primary refrigeratingcircuit, said secondary circuit carrying a refrigerating medium to whichthe temperature conditioned flow from said evaporator is provided, saidsecondary circuit comprising:

a main circuit;

an auxiliary circuit operatively coupled with said main circuit; and

an adjustable valve for controlling flow of the refrigerating mediumbetween said main circuit and said auxiliary circuit,

wherein said auxiliary circuit comprises (i) at least one heat transferdevice for receiving said refrigerating medium and cooling air to befeed into the vehicle interior, and (ii) an inner heat exchangeroperatively coupled with said heat transfer device for increasing thetemperature of the refrigerating medium provided to said heat transferdevice.

In accordance with an additional aspect of the invention, there isprovided a method of air conditioning air in a vehicle, comprising thesteps of:

providing a temperature conditioned flow from an evaporator of a primaryrefrigerating circuit to a refrigerating medium flowing in a secondaryrefrigerating circuit;

feeding said refrigerating medium to an inner heat exchanger positionedin said secondary circuit;

heating said refrigerating medium by said inner heat exchanger;

providing said heated refrigerating medium via a feed to a heat transferdevice; and

cooling said refrigerating medium by said heat transfer device.

Further objects, features and advantages of the present invention willbecome apparent from the detailed description of preferred embodimentsthat follows when considered together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in detail below with reference to theexemplary embodiments and with reference to the accompanying drawings,in which:

FIG. 1 shows a schematic representation of a first exemplary embodimentof a device according to the invention for cooling a motor- vehicleinterior;

FIG. 2 shows the auxiliary circuit from FIG. 1;

FIG. 3 shows another embodiment of the auxiliary circuit according tothe invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to the invention, an inner heat exchanger is provided in theauxiliary circuit, allowing heat exchange to take place between an inletand a return. There is no longer a circulation pump in the auxiliarycircuit, thus allowing corresponding cost savings. By virtue of theinner heat exchanger, the refrigerating medium is heated in the feed. Ahigher flow rate in the auxiliary circuit is therefore set in thefour-way valve in order to achieve the predetermined air temperaturedownstream of the heat transfer device. Because of the higher flow rate,icing and stratification of the air can be avoided. Before therefrigerating medium is returned to the secondary circuit, it is cooleddown by the same amount as it was heated in the feed.

However, this increase in the feed temperature, which is desired in apart-load operation, leads to unwanted losses of capacity in full-loadoperation of the heat transfer device, when the auxiliary circuit isfully coupled to the main circuit and the flow of refrigerating mediumin the main circuit is passed completely through the auxiliary circuit.To minimize these losses of capacity, a refinement of the inventionmakes provision for the return to have a branch between the heattransfer device and the inner heat exchanger, and for the first arm ofthe branch to open into the four-way valve, bypassing the inner heatexchanger, and for the second arm to be passed through the inner heatexchanger and to open directly from the latter into the main circuit,downstream of the four-way valve. The majority of the flow ofrefrigerating medium will then flow via the first arm and bypass theinner heat exchanger owing to the inherent flow resistance of the innerheat exchanger, with the result that little heat exchange takes placeand the temperature in the feed is raised only slightly.

To maximize this effect, the flow resistance on the return side of theinner heat exchanger is significantly greater than the flow resistanceof the first arm of the return in an advantageous refinement of theinvention.

In the part-load operation, i.e. when only a small proportion of theflow of refrigerating medium is diverted into the auxiliary circuit, thefour-way valve is set in such a way that, on the one hand, only thesmall proportion is diverted and, moreover, on the other hand, only asmall amount of the flow of refrigerating medium can be fed back intothe main circuit at the four-way valve. This means that the flowresistance of the first arm is increased owing to the four-way valve,and most of the refrigerating medium in the return flows via the secondarm and hence through the inner heat exchanger and directly into themain circuit. But this means that the desired inner heat exchangebetween the feed and return is achieved in the case of small flows ofrefrigerating medium in the auxiliary circuit.

Turning now to the drawings, a device 10 according to the invention forcooling a motor-vehicle interior has a refrigerating unit 12 thatcontains a primary refrigerating circuit 14 comprising a compressor 18,a condenser 20, an expansion element 22 and an evaporator 24 connectedby refrigerant lines 16. A refrigerant dryer and a refrigerant collectorshould of course be provided in a known manner (not shown) in theprimary refrigerant circuit 12.

The evaporator 24 is designed as a refrigerant/liquid heat transferdevice and can be supplied, on the one hand, with the refrigerant in theprimary refrigerating circuit 14 and, on the other hand, with arefrigerating medium circulating in a secondary circuit 26, allowing thecold produced in the evaporator 24 to be transferred to therefrigerating medium in the secondary circuit 26. The temperature of therefrigerating medium cooled down in this way can be well below 0° C.

The refrigerating medium can be any suitable refrigerating medium asspecific to a given application. For example, a water/glycol mixture ofthe kind customarily used in engine cooling circuits is preferably used.Circulation of the refrigerating medium in the secondary circuit 26 isensured by means of a circulation pump 28.

The secondary circuit 26 furthermore has a control and distribution unit30, by means of which a first adjustable proportion of the flow ofrefrigerating medium can be fed to an optionally provided cold storagedevice 32 and a second, likewise adjustable, proportion of the flow ofrefrigerating medium can be fed to a heat transfer device 34.

The heat transfer device 34 is used to cool air that can be fed to avehicle interior to provide air conditioning for the vehicle interior.The conditioned air is indicated by an arrow 37. A housing for guidingthe air and further details of the guidance and conveyance of the air,e.g. an air guide housing, blowers, air flaps and the like, are normallyincluded but have not been illustrated for the sake of clarity. The heattransfer device 34 can be part of an air conditioner arranged, forexample, in a dashboard of the motor vehicle and can there replace theotherwise customary evaporator.

The secondary circuit 26 illustrated in FIG. 1 has a main circuit 36 andtwo auxiliary circuits 38 and 40. The main circuit 36 is made up ofrefrigerating-medium lines 42, 44, 46, 48 and 50, line 48 containing thecirculation pump 28. The individual lines 42 to 50 of the main circuit36 are connected to one another by, for example, four-way valves 52, 54and 56, the function and mode of operation of which is described below.In this exemplary embodiment, the control and distribution unit 30essentially contains the four-way valves 52, 54, 56, the circulationpump 28 and the corresponding refrigerating-medium lines 44, 46, 48. Anexpansion tank 58 is provided to ensure that there is always asufficient quantity of refrigerating medium in the secondary circuit 26and that changes in volume when the refrigerating medium is warmed orcooled can be balanced out. Different connection points for theexpansion tank 58 and the pump 28 from those illustrated in FIG. 1 arealso possible.

Via the four-way valve 56, the auxiliary circuit 40, which is shownseparately in FIG. 2, can be coupled to the main circuit 36 or separatedfrom it. The auxiliary circuit 40 comprises a feed 60, the heat transferdevice 34 and a return 62. The feed 60 and the return 62 are passedthrough an inner heat exchanger 80, with the result that heat exchangetakes place between the feed 60 and the return 62 and the temperature ofthe refrigerating medium in the feed 60 is raised. To obtain therequired capacity from the heat transfer device 34, a higher flow ratemust be set as compared to a circuit without an inner heat exchanger 80.The higher flow rate reduces the susceptibility to gradients in theauxiliary circuit 40.

Each of the four-way valves 52, 54 and 56 has a rotary slide 72, and asa function of the angular position of the slide four ports a, b, c and dof each four-way valve can be connected to one another in a suitablemanner, preferably in an infinitely variable manner, thus allowingdifferent proportions of the flow of refrigerating medium to flow from ato b and/or a to d and/or d to c and from c to b in the four-way valve56, for example, depending on the position of the rotary slide.

Via the four-way valve 56, the auxiliary circuit 40 can be coupled tothe main circuit 36, which contains the cooled refrigerating medium, andthe extent of this coupling can vary depending on requirements in anygiven application. In the position of the four-way valve 56 shown inFIG. 2, the ports a and b are connected to one another, as are ports cand d, and a proportion of the refrigerating medium can furthermore flowfrom a to d, and, in a corresponding manner, from c to b, the proportionof the flow of refrigerating medium transferred depending, as has beendescribed, on the angular position of the rotary slide 72 of thefour-way valve 56. This proportion of the flow of refrigerating mediumdiverted from the main circuit 36 is fed back to the main circuit 36 inthe transfer from c to b.

With this constitution, the required refrigerating capacity of the heattransfer device 34 can be adjusted up to the maximum possiblerefrigerating capacity. The maximum possible refrigerating capacity isreached when the rotary slide 72 of the four-way valve 56 is in aposition in which only ports a and d and ports b and c are connected toone another, respectively, and the entire flow of refrigerating mediumis passed through the auxiliary circuit 40. However the maximumrefrigerating capacity of the heat transfer device 34 (full-loadoperation) is reduced by the inner heat exchange between the feed andreturn.

In a preferred refinement of the auxiliary circuit 40, which isillustrated in FIG. 3, a higher maximum refrigerating capacity can beachieved. In this embodiment, the return 62 has a branch 82 between theheat transfer device 34 and the inner heat exchanger 80. A first arm 84of the branch 82 opens directly into the four-way valve 56 at port c,bypassing the inner heat exchanger 80. A second arm 86 is passed throughthe inner heat exchanger 80 and opens directly from the heat exchanger80 into the main circuit 36, more specifically downstream of thefour-way valve 56.

The flow resistance on the return side of the inner heat transfer device80 is significantly greater than the flow resistance of the first arm,with the result that, when the four-way valve 56 is set to fullrefrigerating capacity, as illustrated in FIG. 3, the majority of theflow of refrigerating medium will flow through the first arm 84,bypassing the inner heat exchanger 80, thereby increasing the maximumrefrigerating capacity compared with the embodiment in FIG. 2.

When the four-way valve 56 is set to a low refrigerating capacity(part-load operation), i.e. when only a small proportion of the flow ofrefrigerating medium is diverted into the auxiliary circuit 40, and thefour-way valve 56 is set in such a way that only a small proportion canflow from a to d and from c to b, the flow resistance during transferfrom c to b will be relatively high, with the result that in this casethe flow of refrigerating medium in the return 62 will not flow via thefirst arm 84 but via the second arm 86, thereby ensuring a desiredincrease in the heat exchange in the inner heat transfer device 80during part-load operation in this embodiment too.

To illustrate and explain the mode of operation of the device accordingto the invention in the embodiment shown in FIG. 3 in full-loadoperation and in part-load operation, typical values for temperature andflow rate are given below, though the temperature and flow rate can beset accordingly for any specific application:

Full load Cooling a flow of Part load air of 10 kg/min Cooling a flow ofair from 40° C. to of 3 kg/min from 30° 14° C. C. to 7° C. Flow rate inthe main circuit 800 l/h 800 l/h Temperature of refrigerating 10° C. −8°C. medium in the main circuit upstream of the valve Temperature in thefeed 10° C. −8° C. upstream of inner heat exchanger Temperature in thefeed 10.1° C. 0.3° C. downstream of inner heat exchanger Flow rate inthe feed 800 l/h 62 l/h Temperature in the return 14° C. 22° C. upstreamof inner heat exchanger Temperature in the return in 10.2° C. −5° C. thesecond arm downstream of inner heat exchanger Flow rate in the secondarm 17 l/h 19 l/h

The accumulator auxiliary circuit 38 can be connected to the maincircuit 36 in the same way by means of the four-way valve 54 andcomprises a refrigerant-medium line 66, a cold storage device 32 and arefrigerant-medium line 68. As a further option, though not necessary, athird circulation pump 70 can be provided in the accumulator auxiliarycircuit 38 to enable a particular mass flow to be maintained in theaccumulator auxiliary circuit 38.

The disclosure of German Patent Application No. 100 19 580.6, filed Apr.20, 2000 is hereby incorporated by reference in its entirety.

The foregoing embodiments have been shown for illustrative purposes onlyand are not intended to limit the scope of the invention which isdefined by the claims.

I claim:
 1. A cooling device for cooling an interior of a vehicle,comprising: a primary refrigerating circuit comprising an evaporator forproviding a temperature conditioned flow; and a secondary circuitoperatively coupled to said primary refrigerating circuit, saidsecondary circuit carrying a refrigerating medium to which thetemperature conditioned flow from said evaporator is provided, saidsecondary circuit comprising: a main circuit; an auxiliary circuitoperatively coupled with said main circuit; and an adjustable valve forcontrolling flow of the refrigerating medium between said main circuitand said auxiliary circuit, wherein said auxiliary circuit comprises (i)at least one heat transfer device for receiving said refrigeratingmedium and cooling air to be feed into the vehicle interior, and (ii) aninner heat exchanger operatively coupled with said heat transfer devicefor increasing the temperature of the refrigerating medium provided tosaid heat transfer device.
 2. The cooling device of claim 1, whereinsaid adjustable valve is a four-way valve.
 3. The cooling device ofclaim 2, wherein said adjustable, four-way valve further comprises arotary slide.
 4. The cooling device of claim 2, wherein said auxiliarycircuit further comprises a feed for flow of said refrigerating mediumfrom said inner heat exchanger to said heat transfer device, and areturn for flow of said refrigerating medium from said heat transferdevice to said inner heat exchanger.
 5. The cooling device of claim 4,wherein said return comprises a first branch arm bypassing said innerheat exchanger and opening to said adjustable valve.
 6. The coolingdevice of claim 5, wherein said return further comprises a second brancharm passing to said inner heat exchanger, and bypassing said adjustablevalve and opening into said main circuit downstream of said adjustablevalve.
 7. The cooling device of claim 6, wherein a flow resistance insaid second branch arm leading to said inner heat exchanger issignificantly greater than a flow resistance in said first branch arm.8. The cooling device of claim 1, wherein said auxiliary circuit furthercomprises a return line for returning refrigerant from said auxiliarycircuit to said main circuit.
 9. The cooling device of claim 8, whereinsaid return line connects said heat transfer device to said main circuitand passes through said inner heat exchanger.
 10. The cooling device ofclaim 9, wherein said return line comprises a first branch that bypassessaid inner heat exchanger and opens directly into said adjustable valve.11. The cooling device of claim 10, wherein said return line furthercomprises a second branch that passes through said inner heat exchanger,bypasses said adjustable valve and opens directly into said maincircuit.
 12. The cooling device of claim 1, wherein said secondarycircuit further comprises a control and distribution unit forcontrolling flow of refrigerating medium in said secondary circuit,comprising at least one circulation pump for circulating saidrefrigerating medium.
 13. The cooling device of claim 1, wherein saidsecondary circuit further comprises an expansion tank for controlling aquantity of refrigerating medium in said secondary circuit andcontrolling volume changes based on temperature changes in saidrefrigerating medium.
 14. The cooling device of claim 1, furthercomprising a second auxiliary circuit operatively coupled to said maincircuit, said second auxiliary circuit comprising a cold storage device.15. The cooling device of claim 1, wherein said primary circuit furthercomprises: a compressor operably coupled to the output of saidevaporator; a condenser operably coupled to the output of saidcompressor; and an expansion element operably coupled to the output ofsaid condenser.
 16. A vehicle air conditioning unit comprising: acooling device comprising: a primary refrigerating circuit comprising anevaporator for providing a temperature conditioned flow; and a secondarycircuit operatively coupled to said primary refrigerating circuit, saidsecondary circuit carrying a refrigerating medium to which thetemperature conditioned flow from said evaporator is provided, saidsecondary circuit comprising: a main circuit; an auxiliary circuitoperatively coupled with said main circuit; and an adjustable valve forcontrolling flow of the refrigerating medium between said main circuitand said auxiliary circuit, wherein said auxiliary circuit comprises (i)at least one heat transfer device for receiving said refrigeratingmedium and cooling air to be feed into the vehicle interior, and (ii) aninner heat exchanger operatively coupled with said heat transfer devicefor increasing the temperature of the refrigerating medium provided tosaid heat transfer device.